The term defibrotide (hereinafter DF) normally identifies a polydeoxyribonucleotide that is obtained by extraction from animal and/or vegetable tissues (1, 2) but which might also be obtained synthetically; the polydeoxyribonucleotide is normally used in the form of an alkali-metal salt, generally a sodium salt, and generally has a molecular weight of about 15-30 kDa (CAS Registry Number: 83712-60-1).
Defibrotide has the following formula of random sequence:P1-5,(dAp)12-24,(dGp)10-20,(dTp)13-26,(dCp)10-20,wherein                P=phosphoric radical        dAp=deoxyadenylic monomer        dGp=deoxyguanylic monomer        dTp=deoxythymidylic monomer        dCp=deoxycytidylic monomer.Defibrotide corresponding to this formula shows the following chemico-physical properties: electrophoresis=homogeneous anodic mobility; extinction coefficient, E1cm1% at 260±1 nm=220±10°; extinction reaction, E230/E260=0.45±0.04; coefficient of molar extinction (referred to phosphorus); ε(P)=7.750±500; rotary power [α]D20°=53°±6; reversible hyperchromicity, indicated as % in native DNA, h=15±5; and a purine:pyrimidine ratio of 0.95±0.5.        
DF is used mainly on account of its antithrombotic activity (3), although it can be used in other applications such as, for example, the treatment of acute renal insufficiency (4) and the treatment of acute myocardial ischaemia (5). DF is also used in the treatment of emergency clinical conditions, for example, for suppressing the toxicity correlated with high doses of chemotherapy regimens, in particular, the hepatic veno-occlusive syndrome (10, 11); DF has been shown to have protective action towards apoptosis induced by fludarabine and towards the alloactivation of endothelial and epithelial cells, without also altering the antileukaemic effects of fludarabine (12); pre-clinical data also exists on the protective effects of DF that have been achieved in a model of endothelial damage mediated by lipopolysaccharide (13).
A method of producing DF that can produce a product which has uniform and well-defined physical/chemical characteristics and which is also free of possible undesirable side effects is described in U.S. patents (6, 7).
Within the purposes of the present invention DF is either of extractive or of synthetic origin.